I'll try to refrain from adding any more shit to the storm, but I'd also have to disagree. Gay, lesbian, and bisexual aren't physical desires or feelings by themselves either. They refer to physical desires and feelings that a person might have. It's a similar thing with polyamory and monogamy. A polyamorous person wants to experience multiple concurrent relationships, and most would be miserable in total monogamy.

I don't think that by calling it an orientation, anyone is trying to say that being polyamorous is the same thing as being gay with the same kinds of struggles and feelings. I do think there's enough overlap to use some of the same terminology, and that orientation is a reasonable word to use.